The Exact Colour of Doubt
by shred01
Summary: Beckett goes undercover and Castle doesn't like it. Set in season 5. Spoilers for all US-aired episodes.
1. Red

**Title: The Exact Colour of Doubt**

**Author: shred01**

**Spoilers: All aired episodes.**

**Summary: Beckett goes undercover and Castle doesn't like it. Set in season 5._  
_**

**A/N: All mistakes (spelling or otherwise) are my fault.**

**Disclaimer: Castle, sadly, doesn't belong to me. Maybe one day. Till then, I'm just pretending.**

* * *

Castle didn't like this. He didn't like this at all.

In the tight confines for the NYPD surveillance van, Castle watched from his seat at the back as Esposito mic-ed up Kate. She was wearing that black dress that he liked. The one that fell to the floor and had a slit up to her left thigh and showed off her slender shoulders and back. The one that had a neckline that left little to the imagination.

Her hair fell forward, framing her face as she bowed her head and spoke softly to Esposito, directing him on where to go with the wires. The other detective was kneeling in front of her, wires in his hand, carefully threading them along the inside of her right thigh. Epso's face was furrowed in concentration as he took extra care in not letting his fingers slip or touch anything he shouldn't touch as he taped the wire to her skin. His eyes were focus solely on the task at hand and nothing else. He looked at little uncomfortable, knowing that Castle was watching him like a hawk. One wrong move and Castle would be on him. Castle didn't fail to let him know that.

"_I'm watching you," he said. "You look like you're enjoying it, I'm throwing you out of the van while it's still moving."_

_Espo clapped his shoulder in reassurance. "Don't worry, bro. Beckett is like a sister to me. It'll be weird if I tried to cop a feel."_

Usually, stuff like this wouldn't have bothered him. He trusted Esposito but something about this case had him on the edge. He had been nervous ever since Gates gave them the go ahead with the operation. Castle couldn't quite put a finger as to what bothered him so much. He had been through worse, seen worse. However, lately, any case that hit closer to home had Castle jumpy. As if his whole body was on edge, expecting the worst case scenario.

Castle caught the tech guy, who was sitting beside Kate and Esposito, gawking. Now Castle wished he had the same talk he had with Espo with _him_. Even though he was facing the bank of monitors in front of him, his gaze kept slanting towards Kate in that black dress. Now and then, Castle could see his beady little eyes roaming Kate's bare thigh as she hitched her dress up a little higher for Esposito to gain better excess.

Castle balled his fingers into a tight fist, doing everything he can to stop himself from punching the tech guy right in the face. Castle cleared his throat. Loudly. Kate and Esposito glanced at him. The tech guy snapped his eyes to one of the monitors, paling slightly. _Good_. "All set?" he asked the two detectives, he let his gaze linger on the tech guy a little longer before turning it to Kate and Esposito.

"Almost," Esposito said as he climbed to his feet. After a few more twists and turns and maneuvering of the dress, Kate was all done. She spoke low into the mic that was nestle between her breasts. The tech guy played on his keyboard for a moment before giving her gave a thumbs up. Esposito handed her an earpiece and a small handgun before turning his attention to the tech guy.

Kate turned to Castle and smiled. "You ok?" she asked softly as she took a step closer to him.

Castle looked up and returned her smile, saying, "Couldn't be better." Kate raised her eyebrows in skepticism but Castle didn't bother to reassure her.

"Can you help me with this?" she asked, handing him the gun. The small weapon was in its hostler that had Velcro straps on it.

"Sure," Castle mumbled as she parted the slit of her dress wider and presented him her thigh. Castle leaned forward while she placed her hand on his shoulder, bracing herself against him. He took his time strapping the gun.

"You know that this is all your fault right?"

Oh he knew alright. Him and his bright ideas. He should have just shut his mouth and let her lead the investigation like she has always done. But no. He had to open his big mouth and complain that sitting in the car, watching the suspect go in and out of his home, was boring. This case needed more action, he said.

"_And what kind of action would that be, Castle?" Kate asked as she watched David Robins climbed out of his black Audi and made his way towards his brownstone home. _

"_We are not going to find anything about this guy by just sitting in the car and watching him. For the past three days, we only know that he changes his car as often as I change my underwear and he comes home with a different girl every night – all of them brunettes."_

"_What's you point?" Kate asked, glancing at him warily. _

"_My point is, there's nothing we can do with that information."_

"_Yeah, well, unless you have a better idea, this is the only thing we _can_ do."_

_Excitement ran through Castle as an idea popped into his head. "Oh I do have a better idea."_

"Yeah, I know," Castle replied as he tightened one of the Velcro straps. He let his fingers brushed lightly against her skin as he moved to the next strap.

Kate shifted, her hand travelling up his shoulder to the crook of his neck. Her thumb grazed his skin, brushing through the fine hairs there. "So don't be all pouty."

Castle lifted his eyes to Kate's. Though it was dark in the van, Castle caught her smirk. "I'm not being pouty," he said, scowling.

"No, that's an understatement. You look like you want to rip Steve's throat out."

"Who the hell is Steve?" Kate nodded to the tech guy behind her. Castle rolled his eyes. "Right. Well, _Steve_ was leering. At you."

Kate laughed. "He's harmless." The strapping was done but he didn't remove his hands. He let them slid further up her thigh and felt goose bumps raise beneath his touch.

Kate's grip tightened against his pulse point as her eyes fluttered. "Castle," she breathed. Though her tone carried a warning, her eyes betrayed her true emotion.

Ignoring her, he asked, "Are you sure about this?"

Kate took a step back, their hands falling away from each other. "I'll be fine."

Castle stood, his gaze holding hers steady. "Ok, but if _anything_ goes wrong…"

She smoothed out her dress as she replied, "I'll shout out for my knight in shining armor. And for you."

"That's all I ask."

"We're good to go," Esposito announced.

"I'll be fine," Kate repeated, softly. She tugged on the lapel of his coat, smiling, before turning away. He watched as Esposito helped her out of the van. Castle took a seat beside the tech guy – _Steve was it?_ – and watched Kate through one of the monitors. They didn't have a camera on her so the only visual Castle had was of Kate walking from the van to the Robbins' brownstone where she was meeting him for dinner. As soon as she stepped inside, they would only have audio surveillance and nothing else.

"_Mic test,"_ came Kate's voice through the headphones Castle had on.

"We read you loud and clear, Detective Beckett," Steve said through his microphone.

Castle felt a hand land on his shoulder, making him jump slightly. Esposito towered behind him. "You're in my seat, bro."

"Oh right." Castle pulled off the headphones and vacated the chair.

"_Any visual?"_ He heard Kate say, voice tiny and muffled now that he didn't have the headphones on.

"Nothing out of the ordinary," Steve replied as Esposito took his seat beside him. Castle dragged a chair from the back of the van and sat between the two cops. He placed both elbows on the back of their chairs and leaned forward, not wanting to miss a word.

Esposito glanced at him for a brief moment before speaking into his mic. "Ryan?"

"_All clear,"_ came Ryan's voice from Espo's headphone. The detective was considerate enough to have the headphone hang around his neck so Castle could hear everything that was going on. Ryan was sitting in his car at the end of the street, making sure they weren't going to run into any surprises. They still weren't sure whether Robbins worked alone or with a partner.

"Alright, boys. I'm going in," Kate said. A moment later, Castle saw her knocking on the door of the brownstone through one of the monitors. Within seconds, the door open and he caught a glimpse of Robbins before Kate was ushered in. The door closed behind her.

Castle glanced at Esposito expectantly. When he didn't say a word, Castle asked, "That's it?"

Esposito raised an eyebrow but didn't look at him, his attention on the monitors. "What's it?"

"You're not going to say – I don't know – 'the Eagle's in the nest' or something fancy like that?"

This time Esposito did look at him, confusion written all over his face. "What? Why would I say that?"

"That's what all the cops in the movies say."

Esposito shook his head, turning his attention back to the screens in front of him. "No, cops in _real life_ don't say that. Besides, why would an _eagle_ be in a nest?"

Caste shrugged. "It just sounded fancy." Even though the detective had his back to Castle, he could practically see the eye roll. He heard the tech guy snicker beside him and Castle shot him a dark look, quietening him. The three of them fell silent as they listened to Kate and Robbins have their date. Which basically meant that Castle had to listen to Robbins flirt openly with Kate. _His _Kate. Oh and it didn't end there. He had to listen to her flirt _back_.

He didn't know which was worse.

Their dinner went on for about an hour. They talked about his work – he was a college TA who recently came about a large sum of money when his father died nine months ago – and they talked about her work – she was an aspiring artist. They mused about how funny it was that they ran into each other in a gallery opening, especially when Robbins wasn't much of an art fan. He asked whether their meeting was fate. Castle snorted.

It wasn't fate. It was timing. Robbins was known to troll art gallery openings for his victims. He had a soft spot for artsy brunettes. He would invite the girl for coffee first. Then for dinner. On their third date, he would invite her to his place for dinner where he'll rape and murder them all in the same night.

In the past week alone, he left three bodies for the NYPD to find but they could never find enough evidence to convict him. He always seemed to have an alibi – which made them think he wasn't working alone – and not enough evidence for these killings. They needed more and they believe that they were able to find more evidence in his home.

After the first date with Kate, Castle had decided that he didn't like this Robbins guy – not that he was likable in the first place. Since their first two dates were in public places, they were able to watch Robbins and by watching him interact with Kate, Castle knew that Robbins was the scum of the universe.

Castle didn't like the way Robbins touched her or let his eyes roamed her body. He didn't like how close he sat with her or how he always seem to have a hand on her chair as if to keep her rooted in place. He didn't like the questions Robbins asked and how Robbins would dodge questions about himself.

And then there were the little things – the clothes he wore, the cars he drove, the company he kept. Robbins reminded Castle a bit of himself – back when he was the playboy partyer. He knew how guys like that work.

Now that Kate and Robbins were in the privacy of his own home, they didn't have the luxury of video surveillance and had to just rely on audio. And because of that, Castle had been on edge since the night began. He knew what Robbins was capable of and he hated not being able to see what Robbins is doing behind closed doors. What will he do now that he wasn't in public?

"_So you ready for dessert?"_ Robbins asked. There was a tone in his voice that told Castle that Robbins wasn't just talking about cake.

"_Sure. But first, can I use your bathroom? I would like to freshen up before we continue the night,"_ came Kate's reply.

Castle could practically hear the grin in Robbins voice as he said, _"Of course. It's just down the hall – second door on your right." _

There was the sound of movement and a minute later, Kate's voice came spilling through the headphones. _"I found his room."_

"Roger that," Esposito replied.

"_Everything seems to be standard here – nothing out of the ordinary…walk-in closet…dresser by the bed…bathroom."_

Castle couldn't help but think about what Robbins was up to while Kate was rummaging around his bedroom. Was he sharping his knives? Finding that perfect rope? Drugging her wine? Adding poison to her dessert?

Castle gritted his teeth. Why did he have to torture himself like this?

"_Everything seems to be ok. Nothing out of the ordinary."_

"Get out of there befo –"

Espo glared at him over his shoulder and Castle immediately shut his trap. "Dude!"

"Sorry," he mumbled.

"_Hey, everything alright?"_

Castle froze in his seat when the voice that came through didn't belong to Kate.

"_Oh I'm fine. I must have gotten turned around."_

"_Really? If I didn't know better, I thought you were just very curious about the bedroom." _Kate laughed and Robbins chuckled with her. _"How about I give you a tour of the place? That way you won't get caught snooping?"_

Esposito and Castle exchanged worried looks. It was difficult to tell whether Robbins was joking or not.

"_You know that sounds great but it's late. Maybe we can do the tour another time. I should get going anyway,"_ Kate was saying.

"_So soon?"_

"_Yeah, early start tomorrow but I had a great time. Dinner was great. You were great."_

Robbins chuckled and when he spoke, his voice was louder, nearer. _"How about we skip the whole next time and get right down to it?"_

Kate laughed but Castle didn't miss the undercurrent of nervousness in the sound. _"It's late. Maybe some other time," _she repeated, this time a little forcefully.

"_Come on, Katherine, just stay a little while longer. We still have more dessert to get through."_

"_We'll save that for later,"_ Kate whispered teasingly. It was obvious that she was trying to distract Robbins. Castle hoped it wasn't all that obvious to Robbins himself.

Nothing was said after that. The only sound Castle could hear was the rustle of fabric against fabric and his mind started conjuring images that he wished it didn't. "Something's wrong," he whispered to Esposito.

"Hang tight, bro," Esposito said as he fiddled with a knob on the dash in front of him – probably turning the volume up. Was Esposito _trying_ to kill him? The last thing he wanted to hear was the sound of clothes ripping from Kate's body _at a higher volume_.

"No, I mean it. Get her out of there. I don't like the sound of this."

Esposito shot him a look over his shoulder. "Everything's fine. She got this under control, if she didn't she would give us the signal."

"Maybe she's trying to fine the weapon on the guy's body," the tech guy cracked, grinning as he looked at Esposito. "You know, a full body search."

Esposito's expression darkened as he caught the tech guy's gaze. "Shut your mouth."

Castle clapped the tech guy on the shoulder and gave it a hard squeeze. "Listen – Steve is it? – why don't you try to find a way to see if we can hear more?"

Steve's eyes went to Castle's hand before flicking to his face. "What? This is all we have." Castle's grip tightened and a smiled almost escaped onto his lips when he saw a flash of pain in the other man's eyes. He looked over to the other detective beside him for help.

"Go," Esposito commanded. Without a second thought, Steve scrambled from his seat and went to the other side of the van. He started fiddling with a bunch of knobs there. Castle took the vacated seat and slipped the headphones on. "Sorry about that," Espo said in a low voice. "He doesn't know."

Castle grunted his response as he focused his attention on the audio.

"…_Katherine …"_

"Did you hear that?" Castle asked, alarmed. Was that a _moan_?

"Yeah but –"

Castle shushed him. His brow furrowed in concentration as his ears strained to hear more.

"_Are you wearing a wire?!"_

The voice exploded in Castle's ear, making him jump.

"Shit," Espo cursed beside him. "Ryan."

"On it," came Ryan's reply.

"_David please…"_

"_What the hell is going on?"_

"_I –"_

There was a noise that sounded like a smack or a slap. Castle's eyes widened. "What going on?" he asked, the tremble in his voice unmistakable.

"Beckett, can you read me?" Esposito said into his mic.

There was silence.

Castle's heart thudded in his chest, almost bursting through. This is not good. His hands flew to the headphones, pressing the ear buds closer to his ear – as if that action alone will help him to hear something. Anything.

"_Fuck."_

Ripping the headphones off, Castle said, "I'm going in."

"Castle, no!"

But Esposito was too slow. Castle was already clambering out of the van, his shoulder bursting through the doors and throwing himself out of the vehicle. His body was on high alert, eyes focused on the front door of the brownstone. He heard Esposito shouting for him but his brain barely registered it. He needed to get to Kate.

Thankfully the front door was unlocked. He barged through and raced up the stairs that led to the apartment. "Kate!" he yelled as he found himself in the living room. "Kate!" He heard a sound, a cry. Of surprise? Of pain? He wasn't sure. He sprinted towards the general direction of the sound, eyes scanning the area, searching desperately. His chest tightened as every minute passed. He felt like he was running out of time.

Leading by instinct, he headed towards the door that wasn't fully closed. A silver of light leaking through the crack between the door and its frame. He slammed a palm against the heavy wooden door. It crashed against the wall, startling its occupants. Robbins was pressed up against Kate, who was pressed against a wall next to the bed. One of his hands had a tight grip on her forearm while the other was sliding up her thigh, getting way to close to her hidden gun. He whipped his head when he heard the door bang open, surprise and anger mixing on his face. Kate looked shock.

The room disappeared.

Rage poured into his blood, filling his veins.

All he saw was David Robbins, the rapist, the murderer.

And his hands.

On Kate.

"Who the fuck –"

Robbins didn't get a chance to finish his sentence as Castle devoured the distance between them, grabbed the man and hauled him off his girlfriend.

"Castle!"

Castle shoved Robbins on the floor and climbed on top of him. Castle's body was humming with energy, with adrenaline. He was so full with anger that he felt like exploding. He needed to let it out somehow or he'll erupt and it would be so difficult to pick up the pieces.

Robbins' eyes widened in terror when he realized what was happening. Gripping the collar of his shirt with one hand, Castle started pummeling.

He heard a scream.

A groan.

Skin broke.

Bones cracked.

Blood poured.

Colours splashed across his vision. Red. White. More red.

He heard footsteps pounding towards him. He heard someone screaming his name again and again and again. He felt hands on him but he didn't stop. He kept swinging. He kept punching. Castle was focused. He was determined. All he saw was Robbins breaking beneath him.

Robbins the rapist, the murderer.

His hands on Kate.

"Castle! Stop! Please!"

Something in Kate's voice snapped him back to reality. He faltered. He felt hands on him again and this time the person was able to pull him away. His legs lashed out as his hands lost its hold on Robbins, hoping for some kind of contact. The hands on him tightened and he felt himself being dragged away. "You fucking touch her again and I will kill you!" Castle roared at Robbins. There was no response from Robbins. He seemed to be unconscious. Or maybe dead.

Castle's breath came out heavy and ragged as he struggled against the firm hold. There was still so much anger to burn. "You got to relax, bro," came Esposito's voice next to his ear. It was then when Castle realized that it was him who was dragging him away from Robbins, away from the room. "If you don't, I'm gonna have to cuff you."

"Take him outside, Espo," Kate commanded. The strong tone in her voice didn't fail to mask the fear that was underneath. Castle lifted his eyes to hers. Whatever anger that was in him disappeared when he caught the look on her face. Something heavy settled on his heart. He went numb.

She looked scared.

Of him.

* * *

"Take a walk, Castle," Esposito commanded as soon as they were outside. "Cool off."

Castle shrugged off his hands, ignoring his order. "Where's Beckett?"

"Castle –"

"Is she ok?" he asked, voice loud and high.

"Dude, she's fine," Esposito replied curtly. "She'll be out as soon as she done cleaning up your mess. Just…wait here. And don't do anything stupid." Without another word or a glance at him, Esposito jogged back into the apartment.

Castle started pacing. He shoved his hands into his pockets and he winced as his raw knuckles scrap against the rough material. He should get them checked out but he didn't care. The pain thrumming through his hand was a welcome distraction. He let the cold New York night cool off his hot skin as he paced in front of the brownstone anxiously. He felt like he was running a fever. His breath puffed out in front of him as he exhaled, trying to calm his thumping heart.

In the distant he heard sirens and moments later, the street was awash with blue and red lights. An ambulance pulled up beside him and two paramedics jumped out with a gurney. Castle decided it was time to put some distance between him and the brownstone. He didn't want to see the paramedics loading Robbins into a body bag.

"Castle!" He turned at her voice and saw Kate stalking towards him. Anger masked her features but Castle could see the hint of disappointment in the furrows on her brow. "What the hell, Castle?" she asked as soon as she was within earshot. Her voice was loud, catching the attention of a couple of uniformed police officers who had just arrived at the scene.

"Are you alright?" he asked, ignoring her question. "Did he hurt you?"

"Don't," she spat. "Don't give me that. This isn't about me."

Castle sighed as he raked a hand through his hair. "Look, I –"

"Did you know what you just did?" she asked. "Did you know how badly you screwed up in there?"

"Is he ok? Is he dead?"

Kate's eyes widened at his question. "Were you _trying_ to kill him?"

"I –"

"Detective Beckett!"

Kate whirled around. Castle lifted his gaze. Gates stood a few feet behind them, hands on her hips, looking every inch the Iron Gates that she was. Castle didn't want to know how she got wind of the situation so quickly. She must have had an ear on them the whole time.

_Shit._

"Let me go and explain to Gates," Castle started saying. Kate turned to face him and the rest of his words died in his mouth.

"You're done here, Castle. Go home and we'll talk about this later," she said. She turned on her heels and made her way towards Gates.

"Kate…!"

"Go home, Rick!" she threw at him without a backward glance.

* * *

_Chapter 2 up soon. Thanks for reading. You're awesome._


	2. Yellow

_**It was fun watching my inbox break with all the alerts for this story. Thank you for the interest and I hope this doesn't disappoint. **_

* * *

Two hours.

Two hours of pacing the length of the loft.

Two hours of arguing with his mother – trying to convince her that everything was fine, that _he_ was fine before she left the loft in a huff, saying she'll be at friends'.

Two hours of arguing with his _daughter_ almost immediately after. His mother must have called Alexis to get her to see if she could get to the bottom of what's wrong. He dismissed her, telling her that there's nothing to worry about.

Two hours of calling the precinct and demanding where Beckett was and demanding an update on the whole situation. No one was forthcoming with answers.

Two hours of trying to take his mind off things by busying himself with a round of Halo, checking his emails, finishing that last bit of Jack Daniels that was in his office.

Two hours.

Before Kate swung the front door of the loft open and came striding in. The door banged against the back wall from the force before slamming shut behind her. Castle froze behind the kitchen island, a jar of peanut butter in his hand.

Kate looked exhausted but mad. Anger curled off her in waves so tangible that Castle could taste it. It stung his tongue, coated his mouth.

She stood in the middle of the loft and planted her hands on her hips. Her hair was pulled into a loose and messy bun and she had one of those NYPD windbreakers on. It was almost three sizes too big that she was practically swimming in it. She stared at him.

He stared back.

Castle had played this game before. With his mother, Meredith, Gina, Paula and even Alexis. He lost every time. Not this time though. This time he was going to make sure he won't be the first one to say uncle.

They stood like that for a full minute. Then two. Then three.

Then maybe for an hour – Castle wasn't sure. All he knew was that his fingers were starting to cramp as his hold around the peanut butter jar grew tighter and tighter as every minute ticked by. Then with a huff, Kate swivel on her heels and stalked towards their bedroom. Castle almost let himself smile in triumphant but before he could give in to savour the small victory, Kate returned with a first aid kit in her hand. Castle set the jar down on the counter top next to his toast. Kate tossed the kit next to the jar. "Clean that up," she ordered, nodding towards his injured hand.

"It's find. It's just a scratch," Castle replied curtly, pushing the kit aside. He used his bad hand to do it as well, proving to her it was indeed fine. That he could use it – even though it hurt like hell and he was pretty sure he broke a bone in his hand. Maybe a couple. But he wasn't going to tell her that. Hell no.

"God, Castle, for _once_ do as I ask!"

Castle narrowed his eyes at her. "It's. Just. A. Scratch." he repeated slowly. There was a beat as the two of them exchanged defiant stares. Then he asked, "Did he hurt you?"

Kate looked surprised at the question. She took a moment to find her voice before saying, "No…no he didn't. He…erm…found the wire so I tried to distract him but he didn't buy it. He then pushed me against the wall and I was going to push him away when…when you came in."

Castle let his eyes roam over her to make sure she was telling the truth. Satisfied, he turned his attention to his sandwich. He started scooping up a generous amount of peanut butter for his toast. The movement hurt but he swallowed down the pain. "What did Gates say?" he asked, almost casually. When she didn't reply immediately, Castle glanced up. She was studying his hands as he made his sandwich, not meeting his gaze.

"Nothing," she finally mumbled.

Castle scoffed. "Nothing? Seriously? Gates said _nothing_?"

"Doesn't really matter what she said."

"It does. I want to know what she said so that we'd know what to do to fix this."

This time, Kate looked at him, squarely in his eyes. "Oh no. There's no 'we', Castle. Just me. _I'll_ fix this. You're done with this case."

Castle's hands stilled. He set the knife down as he stared at her. "What? Don't I get to at least explain –"

"You broke his jaw, Castle. He's pressing charges. You're _done_."

Castle stomach rolled and his appetite vanished immediately. He pushed away his supper. "Was that your call or Gates?"

"Does it matter?" Kate asked, her eyes searching his. There was so much disappointment in them that Castle almost retched.

"No. No, I guess it doesn't," he finally said.

"And I think it's best if you stay away from the 12th for a while – until everything has blown over. You…you need to think about what you've done.

Castle barked out a laugh. This was some sort of a joke right? Was this the punch line or was that coming later? Maybe next she'll tell him he can't write about her anymore_._ "Oh first I'm benched and now you're sending me to my naughty corner to think about what I've done? What am I? A five year old?"

"Gates is on a warpath. We just lost our lead suspect –"

"He had his hands all over you, Kate! A rapist and a murderer had you cornered and you were in trouble. I did what I had to do."

"Castle, that was not your job! I would have given the signal if I needed backup. Esposito and Ryan were my back up. They would –"

"So. What? You expect me to sit in that van with Steve and not do anything?"

"Yes!"

"Fuck, Kate! How can you even say that?"

"It's not protocol."

"He had his hands on you!" Castle roared. He feels like a broken record. A broken record that nobody is listening. When is she going to get it that he doesn't give a damn about protocol when it comes to his girlfriend being in trouble?

Kate closed her eyes and took a deep breath, trying to compose herself. Castle saw her hands shaking slightly by her sides. "Gates is not going to see it that way," Kate told him as she opened her eyes. They were now dark with frustration. "All Gates is going to see is that we lost our lead suspect and even if we tried him, there's not enough evidence to convict him. The jury isn't going to buy it. There's reasonable doubt here. And Robbins…he knows we are on to him and he'll cover his tracks. We lost. _That's _what Gates is going to see. That we lost this case. Because of you."

Castle rolled his eyes, with a slight shake of his head. "Thanks for rubbing it in, Beckett."

"God, Castle, don't you get it?"

"Oh I get it. I screwed up right? I know, I heard you the first time," Castle spat, sarcasm coating his words.

Kate threw her hands up in exasperation. "You beat up a man!"

"I know what I did, Kate! I was there."

"Really? Do you really know what you did? Because you sure as hell don't act like you give a damn!"

"What do you want me to say? That I'm sorry?"

"It's a good place to start as any."

Castle barked out a laugh. "No. I'm not going to apologize for what I did. I'm sorry I screw up the whole undercover operation, I'm sorry we lost our suspect and I'm sorry I got you in trouble with Gates but I'm _not_ going to apologize for hitting him."

"Why did you even hit him?"

"I thought you were in trouble," he replied simply.

"Well, I wasn't! If I was, I would have given the signal. And if I was, you of all people shouldn't be running in there unarmed!"

Castle picked up the plate with the abandoned toast and chucked it into the sink. The clatter of the plate hitting the metal sink echoed around the loft loudly. "Look, I don't think we should talk about this anymore," Castle said with his back to her. "You should go."

"No. I'm not going anywhere until you tell me what the hell you were thinking. That wasn't you, Castle. You'd know better than that to just come charging in."

Castle whirled around, eyes blazing. "I was thinking my girlfriend was in trouble and I needed to get to her. I was thinking I'm not going to let some psycho rapist touch her. I was thinking I'm not going to let a murderer get to my girlfriend like he did the last time."

Kate blinked at him, confusion descending upon her. "What? What are you talking about? What last time?"

_Fuck_.

Castle raked a hand through his hair, squeezing his eyes shut. He suddenly felt really stupid. He wished he could take back everything he said, grab the words that he let out and stuff it back down his throat.

"Castle, don't shut me out here. I want to understand what happened. I can't just let this go. What you did…you really…" she trailed off but Castle knew what she was going to say.

He scared her.

He saw the look on her face when he was being dragged out the room. He didn't think he would forget that anytime soon. It's permanently scarred into his brain. It's something he never wanted to see from her but he did and it was awful. He repulsed himself for making her feel that way.

He dropped his hands. He focused on the wall behind her, searching for the words. His mind was in a mess and he had a hard time picking through his thoughts.

Kate took a step towards him. Her demeanor was different now – less guarded, less defensive. He took in a breath. "Remember my birthday? The fake murder you staged?" Kate nodded. She seemed afraid to say anything just in case it would spook him back into silence. "When you went into that apartment and the murderer got you, I…I thought you were going to die. I thought he was going to kill you and I was going to lose you."

Kate frowned. "Castle, I was never in trouble."

"I know that. _After_. After you told me it was all fake but _before_? Before I knew he was some actor you hired, I thought he was a real murderer. And he had a knife and he had you and when the lights went out, I thought he was going to kill you…and…" Castle paused as he lost his words. The memory of that night rose up within him, causing the all too familiar fear to take root in his stomach, branches sprouting and wrapping around his lungs and chest, making him breathless. He braced himself against the island as he tried to tamp down the fear.

"Castle –"

He shook his head as his eyes bored into the counter top. He needed to get this out before it rots his insides. "And that was after what happened to Alexis," Castle continued. "Within weeks, I almost lost the two people I loved the most. I couldn't let that happen again. I couldn't see what was happening in that room with Robbins so my imagination went wild. I kept thinking about my birthday and…and…I don't know. I kept seeing that night of my birthday over and over again in my head and I thought, this was real. This was actually happening. You are in a room alone with an actual murderer. This wasn't _fake_." A shudder ran through him. His knuckles went white as his hold tightened, making the scratches and bruises on his injured hand stand out even more. Blue, purple, yellow…

There was silence. Neither of them moved for full minute.

Castle almost jumped when he felt fingers on his forearm. He looked up as Kate tried to break his hold on the counter top. He let her pry his hand loose. She reached for the first aid kit. He let her take his bad hand in hers. He let her unzip the kit and pull out the things she needed. He let her clean the scratches. He let her wrap his hand up with the gauze and bandages.

"Why didn't you tell me about this?" she asked so softly that he almost didn't hear them. He caught her words before they fell to the ground. "Why didn't you tell me you felt this way?"

Castle stared at her for a moment, trying to read her. But she had her head down, loose tendrils of her hair that escaped from her bun framing her face as she tended to his injury, eyes downcast. "A practical joke is turning me into a nervous wreck. Do you realize how stupid that sounds?"

"No, it doesn't sound stupid. It's sound very real to me. But Castle, I'm a cop. I'm in danger almost every day. What's different now?"

"Everything," Castle whispered without a beat.

Kate's eyes flicked to him briefly and he saw understanding in them. She returned her attention to nursing his hand. "I think you need to talk to someone about this."

Castle pulled his hand away from her and took a step back. "No, I can handle this. I just need some time."

Kate folded her arms across her chest, frustration seeping back into her face. "Castle, you almost killed a guy. That's not handling it. You might have PTSD from what happened to Alexis and you need to see someone about this."

Castle scoffed as he brushed past her, moving towards the living room. "I don't have PTSD. I wasn't the one who got kidnapped."

"No, but you went through a traumatic thing and I don't think you took the time to properly deal with it."

"I'll take some time off from the precinct like you said. It'll be fine."

"Castle, stop! Look at me."

Castle halted but didn't turn to face her.

"You can't just hope that this would go away. It doesn't work like that – trust me, I know. What if the next time the suspect has a weapon? A knife or a gun? What if he hurts you?"

Castle faced her, folding his arms, straightening. He lifted his chin. "It won't happen again. This was just a…"

"What, Castle? What was it? If you can put a name for what happened, I'll let this slide."

He searched – for a word, for a sentence, for a name, _anything_ – so they could put this to rest once and for all. But his mind went blank because if he was being really honest with himself, there was no word to describe what happened. He couldn't explain his actions because he didn't know who that man was in that apartment.

His stance wavered.

"Please, Rick. Talk to someone. Do this for me." The expression on Kate's face changed, sharpening into determination. He knew that look. She's not going to budge on this so there was no point in arguing with her. However, every cell in his body was screaming in protest. He felt like he was being punished. For what? For protecting his girlfriend? No, he wasn't going to stand here and let her tell him how he feels or what he has.

Instead he clamped his mouth shut, his whole body vibrating with the effort. As much as he wanted to fight with her about this, he knew it was a battle that no one will win. He was just as stubborn as she was. Arguing wasn't going to make things better. He knows how this would go. They'll fight, scream at each other, maybe call each other names. One of them will storm out. One of them won't come back.

So Castle took a step back. He dropped his arms, hands balling into fists, the strapping going taut around his knuckles and shooting pain up his arm. A reminder of the damage. A reminder of what happened. A reminder of what he did. "I should jump in the shower. It's been a long night," Castle stated flatly, looking away but not before he caught the look of utter disappointment on Kate's face.

"Castle –"

"I'll see you in the morning," Castle said. His words were soft but the meaning was loud and clear.

_Go home._

* * *

_The third and final chapter will be up soon. Until then, thanks for reading._


	3. Blue

_**Red - **Anger, love, violence. _

_**Yellow - **betrayal, perception, fear._

_**Blue - **peace, calm, trust. _

* * *

Before she would have went home.

Before she would have given him the silent treatment.

Before she would have stayed away until _he_ comes groveling back to _her_.

That was before everything changed. Before they changed.

Now, she stayed.

Kate marched up to the guest room, trying to get rid of the disappointment and frustration that she felt towards Castle and how out of control things had gotten.

She threw off her dress and scrubbed her makeup off. Since her spare clothes were downstairs in Castle's room, she snagged the dark blue guest bathrobe from the wardrobe and slipped it on.

Kate trudged down to the kitchen to see if she could find anything to eat. Not that she was hungry. She just needed to keep herself busy, keep her mind from going over her argument with Castle. She couldn't help but analyzed everything she said to him and him to her. Her brain went over every word, every tone, every action, wondering whether she had said the right thing.

Plus, it also gave her an excuse to see if Castle would come out of his room after his shower. Though she wasn't sure what he'll say to her if he did. He told her to go home and she did the opposite. Would that make things even worse between them?

No. she wasn't going to think about this. What's done was done. What's said was said. If he comes out, she'll deal. Right now, she'll turn her attention to something else.

And so she focused on making a bowl of cereal for herself. She focused on getting the bowl from the top cabinet. She focused on grabbing the milk from the fridge. She focused on opening the box of cereal that was left on the countertop and shook out a generous amount into the bowl. She grabbed the bowl and went over to the kitchen island, slipping onto one of the bar stool.

She glanced over to the master bedroom. The door was shut and Kate could still hear the water in the bathroom running. She picked at her cereal – all the while keeping both eyes on the master bedroom door, alert for any activity.

An hour passed and there was still no sign of Castle. Kate poured herself a glass of wine when she realized the cereal wasn't going to be eaten and returned to her position. She busied herself by checking the many messages on her phone. Esposito called about ten times while Ryan left about twenty messages. She fired a quick message to the boys saying that she's fine and that she's working things out with Castle, adding that she might not come in tomorrow. After deleting the boys' messages, she found a frantic message from Alexis from an hour ago. Kate sent an "everything-is-fine-nothing-to-worry-about" text to the redhead, hoping she wouldn't press her for more information. Kate wasn't sure what to tell her if she asks.

The second hour was uneventful as the first. Castle was now pottering around the room doing god-knows-what.

She was almost done with her third glass of wine when Kate decided that she was going to call it a night. Clearly, Castle wasn't going to come out to search for her like she hoped he would. Setting her glass in the sink, she cast one last look towards the general direction of the bedroom before heading upstairs.

It has been awhile she last spent the night in the guest bedroom. It brought back memories of bombs and fire and her apartment in shambles – none of it good memories. And here she was again, adding more bad memories to the room.

Kate lay on her back, not bothering to get under the covers, and stared up at the ceiling. She willed her racing mind to quieten down. Though exhausted, her body was like a live wire, charged and alive. She needed to sleep as she knew it was going to be a long day tomorrow but she knew it wouldn't come that quickly.

Instead, she went over the events of the night. Yet again. Did she overreact? Was she right in blaming Castle for the botched operation? If she was being honest with herself, she understood why Castle did what he did. If she was in his shoes, wouldn't she do the same thing? Maybe the reason why she got so mad was because his actions took her by surprise. She had never seen this side of him before. She saw a glimpse but not the whole picture. It made her realise – yet again – that there was still so much about him that she didn't know.

Then there was the whole thing about how her harmless birthday prank might be the trigger to all that has happened tonight. Kate close her eyes, trying in vain to fight off the picture of Castle's face that elbowed its way into her mind as he described to her how scared he felt that night of his birthday. The last time she saw that fear on his face was when he had thought Alexis was dead in a van. It broke her heart then and it broke her heart now. She swallowed as guilt settled in her stomach like a stone, hard and heavy.

Kate opened her eyes and watched the shadows from the traffic below chase each other on the ceiling. Though the drapes were close, moonlight still managed to filter through, painting the room a dark blue colour that made her feel like she was at the bottom of the ocean.

She flittingly wondered if she was ever going to get some sleep…

Kate jolted awake, blinking. The room swam into focus and she wondered for how long she managed to doze off. She dragged herself up to a sitting position, trying to see if she could find out what the time was.

And to check on Castle.

That was when she spotted him sitting by the door, legs outstretched out in front of him and crossed at the ankles. What little light that spilled into the room, cast eerie shadows across his face, making his features a black mask. "Castle?"

"Hey," he greeted, his voice quiet and jagged.

Kate pressed her palms to her eyes, wondering if she was still asleep. She stayed on the bed just to be sure. "Hey. What's wrong?" she asked, dropping her hands to her sides. She gripped the ties to her robe, tightening the knot around her waist.

"I couldn't sleep so I thought I get a drink of water. That's when I saw your shoes by the door and I came searching for you." He paused as he cocked his head. "You didn't go home." The sentence came out more as a clarifying statement than a question.

"No. No I didn't," she replied as she ran a hand through her hair, smoothing out whatever bed-hair she had. "I know you wanted me to but I couldn't leave like that – not after how things ended between us." Castle nodded and Kate thought she saw a ghost of a smile on his lips. It was gone before she could be sure. "How long have you been sitting there?"

He shrugged, letting his eyes fall to his hands. He started playing the bandage on his right hand. "Not long. I didn't want to wake you."

"Are you ok?"

He didn't reply. He kept tugging at the bandage as if it offended him. "I will be," he finally replied.

Kate took in a breath and exhaled slowly. "I think I did this all wrong," she began quietly. "I was thinking like a cop, that's why I got angry. I wasn't…I should have put myself in your shoes. I should have known that you're still going through stuff. I'm sorry." The silence that followed made Kate shift on the bed uncomfortably. She bit her lip nervously, wondering if her apology was a little too late.

"Do you have doubts after what happened?" he asked after a beat. "Do you have doubts about me?"

Kate couldn't help the surprise from springing up on her face. "What? No, of course not."

"I do." Kate frowned, not sure where he was going with this. She opened her mouth to speak but he beat her to it. "If you ask me 5 years ago what kind of man I am, I would have told you without any hesitation. Now? Now, I'm not too sure. The past year itself, I shot a man intending to kill him, – and I know Tyson deserved it so maybe that doesn't count – I tortured a man for information and now…this. I thought I knew who I was but now…"

"You have doubts," Kate finished for him.

"I have doubts," he echoed, his voice empty. He looked up, catching her gaze. Even in the darkness, Kate could see the hollowness in his eyes, like he lost something tonight. Something he might never get back.

"You're a good, kind, caring, passionate man who would do anything for the people he loves," she told him, putting as much fervor as she could behind her words. She needed him to believe in those words just as much as she believe in them, in him. "You always been that man, Rick. I don't think anything has changed."

"Huh. A kind, caring man who beats up a guy?"

"You did what any man in love would do," Kate admitted. "I get that now."

"I'm not going to apologize for hitting him," he told her, defiance loud and clear in his words.

"I know."

"I was scared. And I was really, really angry that he got too close."

"I know."

"And I know you're a cop with a gun who can take care of herself but if any scumbag touches you –"

"I know," she said with conviction because she did know. She understood what he did and why he did it. He loved her.

"So what now?" he asked.

"I don't know. But whatever happens, we'll deal with it like we always do."

Castle nodded, wordlessly.

"It will be ok, Castle. I promise."

He cracked a smile and hope fluttered in her chest. "Thank you for not going home."

She reached out a hand towards him, palms out. "Come to bed, Castle." He looked at her hand for a moment before returning his gaze to her face. They locked eyes. She smiled.

Castle smoothed out the bandages before climbing to his feet. He took her hand and she tugged him towards the bed. "You know there's a perfectly good bed in our bedroom downstairs."

Kate shushed him. "Let's just stay here for a while."

They settled on top of the covers, side by side, his hand wrapped around her waist, pulling her close to him. His body was hard against hers, his muscles still taut with tension. He buried his nose in her hair as she closed her eyes, bringing his right hand close to her chest. Her thumb stroke the top of the bandages, hoping to ease some of the pain.

"I thought I lost you today," Castle whispered against her skull.

"I'm sorry."

"Don't ever do that again."

"I won't," she promised. She felt him inhale her and she let him, hoping her scent would calm him, remind him that she was here. Alive. With him.

"Are you still mad?" he asked.

"I was never mad."

Her body shook as he chuckled beside her. "Liar."

Kate couldn't help the smile that spilled onto her lips. "Ok, I was mad. But I was mostly scared. For you. I never thought I would see that side of you again."

"I know."

"I still think you need to talk to something about this. It won't get any better."

"I know."

"And I'll help you. I'm not running away, I'll be here."

He pressed a kiss into her hair. "I know."

They stayed still in each other's arms, relishing being close with each other again. Kate watched as the room got brighter, the dark blue turning lighter as the sun rose. As the darkness faded away, so did the anger and doubts between them. A quiet stillness fell over them, filling in the gaps the pain and fear left behind as it ebbed away.

"Castle?"

"Hmm?"

"Thank you for having my back in there."

She could feel him smile as he tucked her tighter against his chest. She molded herself against his frame, his body finally relaxed and accommodating.

"Always."

* * *

_****__**A/N: From reading your reviews, I realised we have a different interpretation of the story. To me, this story was about Castle and how the events of season 5 (namely the kidnapping) has affected him and how he is now a completely different person to the one we saw in 1x01 and how he deals with it. **__****__**Nonetheless, **__****__**I hope the ending was still satisfactory. **_

_****__****__**For all your time, interest and reviews for this story, I thank you.**_ I hope you enjoyed reading this as much as I enjoyed writing it. You are awesome. Truly.


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